Primary drivers of dust deposition within a small subalpine watershed

Abstract:

Dust deposition is increasing across the western US, likely as a result of land use and climate change. The impacts on snow energy balance are especially significant because dust affects snow albedo, heating snow and causing earlier snow melt. Quantifying the spatial and temporal distribution and amount (i.e., mass and size) of dust deposited within a watershed can elucidate drivers of radiative forcing. Parameterization of drivers that control snowpack energy balance improve predictive capabilities in hydrological models of water yield from snow. We hypothesized that topographic indices, namely aspect and vegetation cover, will have the greatest effects on dust distribution and will be consistent with prevailing wind direction. We used direct snowpack collection to estimate dust inputs at 19 plots within the 120 ha No Name watershed at approximately 3000 m elevation in the Snowy Range Mountains in Wyoming. Samples were collected, thawed gradually, and filtered. Meteorological, geographic, and biological factors were correlated with dust deposition. Across the watershed, mean dust input was 36.5 ± 3.1 mg. Aspect explained the most variance of dust deposition across the watershed and was associated with prevailing wind directions (R² = 0.70), as predicted. Prevailing northwesterly winds lead to the greatest dust deposition on the southeast slopes. Increased dust deposition rates across southeastern slopes in the Snowy Mountains in Wyoming areas may lead to more rapid snowmelt rates and earlier peak flow. More broadly, understanding the interaction between topography, land use, and dust deposition can help predict snow melt and improve plans for downstream water needs.